Mutant Fish Evolved To Tolerate Polluted, Toxic Waters: Here Is How They Do It

Thanks to its high level of genetic diversity, minnow-like Atlantic killifish has evolved to withstand lethal, human-altered environments. Researchers found that the mutant fish has evolved to be 8,000 times more resilient to this level of toxicity compared to other fish.

Published in the journal Science, a team of scientists at the University of California, Davis, found that Atlantic killifish living in four polluted East Coast bays are resilient to high levels of toxic industrial pollutants that would normally kill them.

The Atlantic killifish spend their entire lives swimming in toxic chemicals in some of the United States' most polluted waters. Now, scientists have figured out why they are thriving despite the highly lethal environments.

Atlantic Killifish

According to the National Geographic, killifish, also called mud minnows or mummichog, are abundant small silver fishes found in the brackish waterways and marshes along the Atlantic coast. They are usually used in aquariums because of their size and beautiful colors.

In the past, this species has been an indicator of the health of ecosystems because they are really sensitive to pollution. However, when the researchers studied those living in polluted areas, they found something strange as the fish have evolved to be resilient to pollution.

How Can These Fishes Tolerate Polluted Waters?

The researchers found that extremely high levels of genetic diversity, even higher than any other vertebrae, has made it possible for them to quickly adapt and evolve to withstand and resist these toxic chemicals. This is why insects could easily evolve and resist pesticides and microorganisms becoming superbugs because they easily resist the drugs that used to destroy them. However, not all species on Earth can do this.

"Some people will see this as a positive and think, 'Hey, species can evolve in response to what we're doing to the environment!'" Andrew Whitehead, the lead author, said in a press release by UC Davis. "Unfortunately, most species we care about preserving probably can't adapt to these rapid changes because they don't have the high levels of genetic variation that allow them to evolve quickly," he added.

Sequencing Genomes

To land to their findings, the scientists sequenced the genomes of about 400 killifish from both polluted and non-polluted locations including New Bedford Harbor in Massachusetts, Bridgeport area in Connecticut, Elizabeth River in Virginia and Newark Bay in New Jersey.

The polluted areas have been flowing with toxic and industrial pollutants since the 1950s and 1960s. The chemicals include heavy metals, dioxin, hydrocarbons and others. They found that the genetic diversity of the fish makes it remarkably well-positioned to adapt and survive in environments that have been radically changed.

"If we know the kinds of genes that can confer sensitivity in another vertebrate animal like us, perhaps we can understand how different humans, with their own mutations in these important genes, might react to these chemicals," Whitehead said.